Hydroformylation is a well known reaction in which an olefin is reacted under suitable temperature and pressure conditions with hydrogen and carbon monoxide in the presence of a hydroformylation catalyst to give an aldehyde, or a mixture of aldehydes, having one more carbon atoms than the starting olefin. For example, a hydroformylation reaction with propylene will yield a mixture of n- and iso-butyraldehydes, of which the straight chain n-isomer is usually the more commercially desirable material. The hydrogen and carbon monoxide will generally be supplied to the hydroformylation reactor as synthesis gas. Examples of hydroformylation processes can be found in U.S. Pat. Nos. 4,247,486, 4,482,749, 4,496,768, 4,496,769, 4,593,127, 4,599,206, 4,668,651, 5,001,274, 5,105,018, 5,367,106 which are incorporated herein by reference.
Cooling in these processes has generally involved (a) typical individual reactor cooling by known internal or external heat exchangers and/or (b) using an external heat exchanger on the process stream of reaction mixture flowing from a first reactor to a second reactor, including cooling with the return of a cooled stream to the original reactor. See FIG. 1. For example, in U.S. Pat. No. 4,247,486 it is taught that the catalyst-containing reaction streams or mixtures are desirably retained in the reactor (and sent to external cooling) to avoid losses.
Rhodium complex catalysts are now conventionally used in the reaction mixtures in the hydroformylation of olefins permitting lower operating pressures and yielding desirable aldehyde product ratios. Since the rhodium catalyst is non-volatile, product recovery and catalyst reuse is greatly simplified. See “Low-pressure OXO process yields a better product mix”, Chemical Engineering, Dec. 5, 1977 and U.S. Pat. No. 3,527,809, GB-A-1338237 and GB-A-1582010 which are incorporated herein by reference. Since rhodium catalysts are so expensive, it is very desirable to utilize this highly expensive metal in the most economically effective way. The reaction solution for the hydroformylation reaction will generally also contain excess ligand which, in many cases, is also very expensive. Therefore, in any cooling of these reactions, catalyst and process fluid losses need to be avoided or minimized.